Various patents disclose apparatus and methods for blow molding hollow thermoplastic containers. See, for example, U.S. Pat. No. 4,707,966 to Weiler et al. which discloses the continuous extrusion through an extruder head of a length of parison in the form of a hollow tube between and through two coacting first or main mold halves. The method includes the step of cutting off the parison below the extruder head and above the main mold halves to create an opening which allows a blowing and filling nozzle assembly to be moved downwardly into the opening in the parison for molding and thereafter filling a molded container.
When the container is filled with the desired amount of liquid, the blowing and filling nozzle assembly is retracted from the opening in the parison. A separate pair of coacting second or upper sealing mold halves are then moved together around the exposed length of parison to form and seal the container upper portion. The finished container, completely formed, filled, and sealed, is then conveyed out of the apparatus.
Of particular interest to the subject of the present invention is the apparatus and method for cutting off the length of parison and creating the opening therein which, according to the method disclosed in U.S. Pat. No. 4,707,966 to Weiler et al., currently involves the use of a heated moving cutter such as a hot wire or the like which melts through and severs the parison.
While this severing apparatus and method has worked satisfactorily in most applications, a potential disadvantage associated with the use of a hot wire or the like is the risk inherent in the generation or creation of parison particulates or vapor and the deposit thereof within the interior of the container or in the surroundings.
The present invention provides an improved apparatus and method for severing the parison which greatly reduces the generation or creation of contaminant particulates.